In existing structure of a battery module, a side plate has a composite structure consisting of aluminum alloy and an insulating membrane, adjacent mono-batteries directly contact with each other or space apart from each other via a compact plate (such as rubber pad, insulating plastic). When one mono-battery suffers thermal runaway, a temperature of the one mono-battery even reaches 500° C., at this time, heat generated by the one mono-battery may be massively transferred to mono-batteries adjacent to the one mono-battery respectively via adjacent compact plates and the side plate of metal (such as aluminum alloy), therefore the mono-batteries adjacent to the one mono-battery are also runaway. However, using an aerogel blanket to space apart the adjacent mono-batteries will cost too much.